Green Synthesis of Silver Nanoparticles Using Aqueous Plant Extracts and their Anticancer Activity against Colorectal Cancer: A Systematic Review

Introduction: Green-synthesized silver nanoparticles (AgNPs) using plant extracts represent a sustainable alternative for cancer therapy, offering targeted cytotoxicity with reduced side effects. This systematic review aimed to evaluate the synthesis, characterization, and in vitro anticancer efficacy of plant-mediated AgNPs against colorectal cancer (CRC) cell lines. Methods: Following PRISMA guidelines, a comprehensive literature search was conducted across PubMed, Scopus, ScienceDirect, and Google Scholar databases from 2010 to 2024. Studies were included if they reported green synthesis of AgNPs using aqueous plant extracts and evaluated cytotoxic effects against CRC cell lines in vitro. Key data, such as nanoparticle size, shape, IC50 values, synthesis parameters, and mechanisms of action, were extracted and synthesized. Results: Nineteen studies met the inclusion criteria. AgNPs were synthesized using over 20 plant species, mostly yielding spherical particles sized between 3.9-76 nm. Potent cytotoxic effects were observed against CRC cell lines, such as HCT-116, HT-29, Caco-2, and SW480. The most effective nanoparticles, with IC50 values <5 μg/mL, were synthesized using Annona muricata and Plumeria alba. Mechanisms of action included reactive oxygen species (ROS) generation, mitochondrial dysfunction, DNA fragmentation, and apoptosis induction. Anticancer efficacy was closely linked to particle size, surface charge, and phytochemical capping. Conclusion: Green-synthesized AgNPs exhibited promising anticancer activity against CRC cell lines, with enhanced efficacy associated with smaller size and bioactive phytochemical coatings. Despite their potential, standardization of synthesis protocols and further in vivo and mechanistic studies are essential to support clinical translation.